The present invention relates to a pneumatic tire. More specifically, the invention relates to a pneumatic tire improved in or relating to both of the cornering performance on dry pavements (hereinafter referred to as the dry-condition cornering performance) and the water removing or repelling characteristic both in straight running service services and in cornering service of the tire on wet pavements (hereinafter referred to as the wet-condition performance).
It is known in the prior art to improve the dry-condition cornering performance by providing to tires a tread pattern which is asymmetric relative to the tread center. In greater detail, in order to attain the intended improvement, tires having such tread pattern are mounted on vehicles in a manner such that the side of the tire in which the groove area ratio on the tread surface is relatively small and the stiffness on the tread surface is relatively high is disposed at an outer side of the vehicles. This is because as follows: While in letting vehicles undergo a turning or cornering, the load on tires tend, due to the centrifugal force generated by the cornering of the vehicles, to concentrate on tires located on the side opposite to the side to which the vehicles are turned, the tread surface on the side of the tire having a relatively high stiffness can stand the concentration of load. However, a problem is indicated of the above tires such that upon cornering of vehicles on wet pavements, the water repelling characteristic lowers in the tread region having a relatively small groove area ratio.
Japanese patent application Kokai publication No. 61-98601 proposes to attain an improvement in or relating to the water removing characteristic upon cornering, by providing a tire having a fletch- or herringbone-type tread pattern which comprises a plurality of straight-linear main grooves extending in the circumferential direction of the tire and a plurality of subgrooves bridging the main grooves and extending toward shoulder ends of the tire and in which the subgrooves include an angled or a curved portion convex in the direction of rotation of the tire, the tire being mounted on a vehicle with the angled or curved portion of sub- grooves disposed on an outer side of the vehicle. This tire can exhibit an improved wet-condition performance not only upon cornering or turning but also in straight running of vehicles. However, it has been impossible to obtain a satisfactory dry-condition cornering performance by way only of providing a herringbone-type tread pattern such as above.